FULL PRODUCT VERSION :
1.6.0_18 (it worked on 1.6.0_17 and several earlier versions though I haven't tried them all)

ADDITIONAL OS VERSION INFORMATION :
Windows XP (no failure occurs on Macintosh (1.6.0_17) and on Windows 7 (1.6.0_18), only fails on XP)

A DESCRIPTION OF THE PROBLEM :
A program installed from our website (sumac.com) using JWS, with offline-allowed in its jnlp file, does not run offline. The jnlp for this program has worked fine for months. Now, the launcher gives Exception:

JNLPException[category: Download Error : Exception: java.net.UnknownHostException: sumac.com : LaunchDesc:
<jnlp spec="1.0+" codebase="http://sumac.com/release32/" href="http://sumac.com/release32/SumacWin.jnlp">
  <information>
    <title>Sumac</title>
    <vendor>Softwood Technology Inc.</vendor>
    <homepage href="null"/>
    <description>Sumac caters to all non-profit organizations.</description>
    <icon href="http://sumac.com/images/SumacIcon32.gif" kind="default"/>
    <shortcut online="true">
      <desktop/>
    </shortcut>
    <association extensions="ssc" mime-type="application-x/sumacSearchCriteria">
      <icon href="http://sumac.com/images/SumacDocIcon32.gif"/>
    </association>
    <association extensions="ssi" mime-type="application-x/sumacSQLImport">
      <icon href="http://sumac.com/images/SumacDocIcon32.gif"/>
    </association>
    <association extensions="srl" mime-type="application-x/sumacReportLayout">
      <icon href="http://sumac.com/images/SumacDocIcon32.gif"/>
    </association>
    <offline-allowed/>
  </information>
  <security>
    <all-permissions/>
  </security>
  <update check="always" policy="prompt-update"/>
  <resources>
    <java java-vm-args="-Xms64m -Xmx128m" version="1.6"/>
    <jar href="http://sumac.com/release32/Sumac.jar" download="eager" main="false"/>
    <jar href="http://sumac.com/release32/mysql-connector-java-5.1.7-bin.jar" download="eager" main="false"/>
    <jar href="http://sumac.com/release32/iText-2.1.5.jar" download="eager" main="false"/>
    <extension href="http://sumac.com/release32/mail.jnlp" name="mail"/>
    <extension href="http://sumac.com/release32/bcmail.jnlp" name="bcmail"/>
    <extension href="http://sumac.com/release32/bcprov.jnlp" name="bcprov"/>
    <extension href="http://sumac.com/release32/derby.jnlp" name="derby"/>
  </resources>
  <application-desc/>
</jnlp> ]
at com.sun.javaws.jnl.JARUpdater.updateCheck(Unknown Source)
at com.sun.javaws.jnl.JARUpdater.isUpdateAvailable(Unknown Source)
at com.sun.javaws.jnl.LDUpdater$RapidUpdateChecker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)


and the console says:
#### Java Web Start Error:
#### Unable to load resource: http://sumac.com/release32/Sumac.jar

and the Wrapped Exception is:

java.net.UnknownHostException: sumac.com
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.net.NetworkClient.doConnect(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.&lt;init&gt;(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
at com.sun.deploy.net.BasicHttpRequest.doRequest(Unknown Source)
at com.sun.deploy.net.BasicHttpRequest.doGetRequestEX(Unknown Source)
at com.sun.deploy.net.DownloadEngine.isUpdateAvailable(Unknown Source)
at com.sun.deploy.net.DownloadEngine.isUpdateAvailable(Unknown Source)
at com.sun.javaws.jnl.JARUpdater.updateCheck(Unknown Source)
at com.sun.javaws.jnl.JARUpdater.isUpdateAvailable(Unknown Source)
at com.sun.javaws.jnl.LDUpdater$RapidUpdateChecker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)



STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
install our app (go to sumac.com, click Support, click to install on windows)

when the program runs, quit

disconnect from the network

try running again; it fails

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
it should run offline since the jnlp says to allow this
ACTUAL -
see Description above

ERROR MESSAGES/STACK TRACES THAT OCCUR :
see Description above

REPRODUCIBILITY :
This bug can be reproduced always.

Release Regression From : 6u17
The above release value was the last known release where this
bug was not reproducible. Since then there has been a regression.